Engine starter



Jan. 6, 1953 0. L. MILLER ENGINE STARTER GEARING Filed May 3, 1951 INVENTQR.

ATTORNEY Patented Jan. 6, 1953 2,624,202 ENGINE" STARTERT'GEARING DonaIdLL. Miller;

Bendix; Aviation Corporation,

Horseheads,:'N. Y., assignon; to-

Elmira Heights,

N. Y., a-zcorporationzof Delaware ApplicationMay 3, 1951, Serial No; 224,285

G GIaims.

The present invention relates to engine starter gearing and more particularly to an automatically engaging drive having means for delaying the demeshing of the drive pinion when the engine fires.

In that form of anti-kickout starter drive such as shown, for instance, in thepatent to Martin. 2,313,656, which incorporates a centrifugallatch rotating with the pinion, it sometimes happens that one or two powerful initial explo sions of the engine-may cause withdrawal of the latch so as to permit demesh of the pinion before the engine is reliably self-operative.

It is'an object of the present invention to provide a novel 'anti-kickout starter drive-in which thedisconnection of the gearing" is controlled primarily by the rotative speed of the engine.

It is another object to provide such a device incorporating a time control feature for delaying the disconnection of the gearing.

It-is another object to provide'such a, device incorporating a centrifugal latch for controlling the demeshing' movement of the gearing, and means for temporarily delaying the release of the latch.

Further objects and advantages will be apparent from the following description taken in connection with the accompanying drawing in which:

Fig. l is aside elevation partly brokenaway and-in section of a preferred embodiment of .the invention" showing the parts in normal for idle position;

Fig; 2 is a similar view showing the parts in the positions assumed when the pinionoverruns the drive as the engine fires Fig. 3 is a, view similar to Fig. 2 of a second embodiment of the invention; and

Fig. 4-is an enlarged sectional detail of the centrifugal latch and time delay structure.

In-Fig. 1 ofthe drawing there is illustrated a power shaft I on which a hollow quill shaft 2 is rigidly mounted as by means of a cross pin 3. A hollow screw shaft 4 is slidably-journaled'on the quill shaft 2, being'retained thereon by an abutment ring 5 bearing against a lock ringfi seated in the periphery of the quill shaft.

Screw shaft 4 is provided with overrunning clutch teeth 1 arranged to cooperate with similar teeth 8 formed on a driving clutch member 9 Whichis also slidably journaled on the quill shaft 2; its longitudinal movement being limited onthe one handby a split lock ring H seatedin the surface of the quillshaft' and on the other-handby aashoulder l2 formed on the quillshaft byran enlarged section adjacent its driving end.

Means for. actuating the driving clutch member 9' from the quillishaft 2. is provided in;the2form of a torsion and compressionspring l3 theturned ends of which engage in slotsin the'anchor plates l4, I51WhiCh' arenon-rotatably mounted on the end-of the quill shaft-.2 and on the drivenclutch member 9 respectively.

A. pinion. I6 is slidably 'journaled o-nthepower shaft l forzmovementiinto and out of meshwith an: engine. gear 1 I; A control nut Li 8 is threaded on thee-screw -shaft 4 and iszconnected to actuate the pinion-by means of a barrel l9 rigidly connected to thepinion as indicated at 2| and keyed to the control nut at its other end as indicated at 22.

The control nut and barrel are provided with a radial. opening 23in which a cylindrical cup member 24is pressed and anchored in any suitable manner. A detent or latch member 25" is slidably mounted in said cup member and has an inwardly-extending:stem 2B bearing on the-sur face of the screw shaft-4. Means for normally pressing the-latch againstthe screw shaft is provided inr-the form of' an elastically compressible dash-pot member indicated generally by numeral' 21'.

Member '21 is-in the form of a capsule or drum closedat-its ends by flexible heads or'diaphragms 28, 29 and having an intermediate partition 3! dividingthe interior into an outer chamber '32 and an inner chamber 33. A spring 34 is located between the partition 3| andthe inner diaphragm 29; normally maintaining; the latter distended so as to bear-on the-latchmember 25"and press it into" engagement with the screw shaftll; A .centralopening 35' is provided in the partition 3|, and'a valve disc 36' having a small aperture 31 is pressed against the inner side of the partition by aspring 38 so as to cause said valve disc to cover theopening.

The. dash-pot 21 is filledwith a suitable liquid such asasilicone oil having a substantially constant viscosity over the operating range-of temperature of the drive.- When the centrifugal force of the latch 25 is sufiicient to overcome the spring 34 and move the latch outward, this movement is delayed by the liquid in theinner chamber:33 which haste passthrough the small opening31 in the valve disc 36 inorder to escapeinto theouter chamber 32. The subsequent return of the -latchinto contact with screw shaft 4 by; the spring 34* is" substantially unimpeded since the A spring 42 and thrust washer 43 are located between the end of the screw shaft 4 and the abutment 5, the said spring functioning to normally hold the overrunning clutch teeth I, 8 in engagement.

In operation, starting with the parts in the positions illustrated in Fig, 1, rotation of the power shaft by the starting motor is transmitted through the quill shaft 2, spring l3, and clutch member 9 to the screw shaft 4, the rotation of which causes the control nut IE to traverse the pinion l5 into mesh with the engine gear II. The travel of the control nut is arrested by the abutment 5, whereupon the screw shaft 4 is forced to the left against the compression of the drive spring l3, which compression. is limited by the shoulder I 2 on the screw shaft. The overrunning clutch teeth 1, 8 are thus forced tightly together so as to transmit the rotation of the power shaft to the pinion t5 and the engine gear ll.

When the engine fires, the consequent acceleration of the pinion l5 causes the pinion with its associated parts to overrun the starting motor, the control nut i8 moving back on the screw shaft 4 so as to permit the overrunning clutch teeth 2', 8 to disengage as shown in Fig. 2. At this time, the stem 26 of the latch engages the shoulder 4! on the screw shaft which arrests the demeshing movement of the control nut and pinion. This action takes place even though the momentary speed of the pinion and control nut is high enough to cause centrifugal force to withdraw the latch. Immediate withdrawal of the latch is prevented by the liquid in the dash-pot 21 trapped in the lower chamber 33 by the valve disc 36.

If the engine should not remain self-operative, as soon as the pinion slows down to the speed of the power shaft, crankingof the engine is resumed. 7

When the engine becomes reliably self-operative the centrifugal force of the latch-25 compresses the diaphragm 29, forcing the liquid through the small aperture 31 in the valve disc 3'6 until the stem 26 of the latch disengages itself from the shoulder ii of the screw shaft, permitting the parts to be returned to their idle positions, When the control nut reaches the end 'of the screw shaft, and its rotation thereon is arrested by the ends it of the threads,the spring 34 of the dash-pot member expands and presses the latch member against thescrew shaft so as to resist any tendency of the pinion to be moved back into engagement with the engine gear.

In the embodiment of the invention shown in Fig. 3 the yielding driving function of spring I3 is performed by an overload slip coupling which coupling also performs the function of controlling the overrunning clutch connection. As there illustrated, a power shaft 5! has fixedly mounted thereon a screw shaft 52 on which a control nut 53 is threaded. The control nut is provided with inclinedteeth54 cooperating with corresponding teeth 55 of an intermediate coupling member 56.

The latter has overrunning clutch teeth 51 which cooperate with similar teeth 58 on a driven clutch member 59, fixedly mounted in any suitable manner on a pinion 61 which is slidably journaled on the power shaft for meshing engagement with an engine gear 62.

The control nut 53 has a radial flange 63 forming an abutment for a plurality of spring discs 64 hearing against a thrust plate 65 locked on the control nut by a lock ring 66 so as to maintain the spring discs under initial compression.

The driven clutch member 59 has a radial flange 61, and a barrel member 68 incloses the coupling and clutch members and has a terminal flange '69 bearing against flange 61. At the other end, the barrel 68 receives the thrust plate 65 which is retained therein by a lock ring H.

A thimble 12 surrounds the adjacent end portions of the control nut 53 and coupling member 55 so as to maintain the coupling member in alignment with the control nut; and a spring 13 located between a flange 14 on the thimble and a flange 75 on the coupling member serves'to normally maintain the overrunning clutch teeth 57, 58 in engagement. 7

Screw shaft 52 is provided with a shoulder 76, and the control nut 53 has a latch and dash-pot structure 71, similar to latch 25 and dash-pot 27 of Fig. 1, mounted thereon in position to engage the shoulder H5 of the screw shaft to prevent demeshing movement of the pinion and its associated parts until the latch is released by centrifugal force. Y 7

It will be noted that in this embodiment of the invention, the overrunning clutch connection is located between the control nut 53 and the pinion 6i so that when the pinion overruns the starting rotated positively at'the same speed as the pinion, as it is in the structure shown in Figs. 1 and 2. It could happen, therefore, if the operator should open the starting switch immediately after the engine fires, that the screw shaft and control nut would not rotate fast enough to release the latch 11 by centrifugal force, and the drive might be held in mesh after the engine was fully operative. In order to provide .for. this contingency, the latch is formed with a tapered nose as illustrated sufficiently so that the pressure of the latch against the inclined shoulder caused by the drag of the overrunning clutch teeth 51, 58 under the pressure of the spring 73 will push the detent out and permit the control nut to thread itself back to idle position after a suitable time delay as controlled by the dash-pot.

In the operation of this embodiment of the invention, rotation of the power shaft 5| and screw shaft 52 traverses the pinion 61 into mesh with the engine gear 62, the meshing position of the control nut being defined by the ends 18 of thethreads on the screw shaft. The consequent rotation of the control nut is transmitted to the coupling member 55 through the inclined teeth 55, 55, the camming action of which compresses the overrunning clutch teeth 51, 58, this action being cushioned by the springs 64. Excessive torque causes the inclined teeth 54,55 to compress springs 54 suITiciently to permit slippage and dissipation of the peak torque. v 7

When the engine fires, the demeshing movement of the pinion 6! is delayed by the latch and dash-pot structure in the same manner as in the first embodiment so as to insure that the engine.

is reliably self-operative before demeshing is permitted to occur.

Although but two embodiments of the invention have been shown and described in detail it will be understood that other embodiments are possible and changes may be made in the design and arrangement of the parts without departing from the spirit of the invention.

I claim:

1. In an engine starter drive a power shaft, a screw shaft rotatably mounted thereon, means including an overrunning clutch for rotating the screw shaft from the power shaft, a pinion slidably journaled on the power shaft for movement into and out of mesh with a member of an engine to be started, a control nut on the screw shaft, a barrel member connecting the control nut to the pinion, said screw shaft having a peripheral notch formed therein, a centrifugal detent mounted to rotate with said control nut and barrel and engageable with said notch in the screw shaft as the pinion approaches its fully meshed position, spring means urging the detent into engagement with the screw shaft and holding it so engaged until the control nut attains a critical speed and means for delaying Withdrawal of the latch from the notch after said critical speed is exceeded for a predetermined time.

2. An engine starter drive as set forth in claim 1, in which the delaying means is in the form of a dash-pot impeding the centrifugal movement of the latch.

3. An engine starter drive as set forth in claim 1, including further a radially extending cylinder fixedly mounted in the control nut inwhich the latch is slidably mounted, and a sealed capsule in the cylinder in the path of the latch in the form of a drum with flexible heads, a partition dividing the capsule into two chambers, and means for controlling the flow of fluid between said chambers.

4. An engine starter drive as set forth in claim 3, in which the capsule is filled with a non-compressible liquid, and the flow-controlling means restricts the radially-outward flow of the liquid through the partition but allows substantial unimpeded flow in the opposite direction; and

- erating with the shoulder yielding means tending to distend the inner head of the drum and hold it in contact with the latch.

5. In an engine starter drive a power shaft, a pinion slidably journaled thereon for movement into and out of mesh with a gear of an engine to be started, means for actuating the pinion from the power shaft including a screw shaft and a control nut having limited longitudinal movement thereon, said screw shaft having a shoulder, and said control nut having a centrifugal latch cooperating with the shoulder to hold the pinion in mesh with the engine gear until the control nut rotates above a predetermined speed; and a dashpot controlling the latch for delaying release of the latch for a time interval after the nut has attained the critical speed.

6. In an engine starter drive a power shaft, a pinion slidably journa-led thereon for movement into and out of mesh with a gear of an engine to be started, means for actuating the pinion from the power shaft including a screw shaft and a control nut having limited longitudinal movement thereon, said screw shaft having a shoulder, and said control nut having a centrifugal latch coopto hold the pinion in mesh with the engine gear until the control nut rotates above a predetermined speed; and means for delaying release of the latch for a time interval after the nut has attained the critical speed; in which the means for delaying release of the latch is in the form of a dash-pot comprising a sealed drum having flexible heads and filled with an incompressible liquid, and a perforated partition dividing the interior of the drum into two chambers and controlling the flow of the liquid from one chamber to the other.

DONALD L. MILLER.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS 

